1. Field of the Invention
This invention relates to pumps and more particularly to a sonic pressure wave pump which is particularly adapted for use in low production wells.
2. Description of the Prior Art
For many years, oil wells which are considered as low production wells, for example, in the range of from four to 10 barrels per day, have been capped in that the costs for pumping such small quantities have far exceeded the returns that could reasonably be expected. Even with the high costs of petroleum products today, pumping such small quantities is still not profitable due to the type of pump mechanisms in general use. The generally used pumps, sometimes referred to as "walking beam pumps", are very expensive from initial cost, operating expense and maintenance standpoints, and as a result, many low production wells remain capped. Another problem with most low production wells is the high gas content which in some instances, will prevent or at least impair, the operation of the walking beam pumps.
For many years now another basic approach in pumps has been proposed which involves imparting intermittent pressure waves on a column of liquid contained in pump tubing which extends from the subterranean source of the liquid to an above ground location. In general, the pressure waves are generated by an above ground mechanism which reciprocally impacts the column of liquid and, in addition, will cyclically open and close a liquid delivery port. Such impacting of the column of liquid produces pressure waves that are transmitted by the liquid to the down-hole pumping device such as a standing valve to impart a reciprocal movement thereto. The down-hole pumping device usually includes a plunger, or similar mechanism, which is biased upwardly by suitable springs and has a central passage formed axially therethrough with a one-way check valve located in the passage. When the hydraulic pressure waves move the plunger down against the spring bias, the check valve opens to admit the liquid being pumped into the passage. And the subsequent upstroke of the plunger closes the check valve and causes a general upward movement of the liquid column with the uppermost portion thereof discharging an amount of liquid, through the delivery port, with the amount being equal to the amount taken in by the down-hole pumping device.
Examples of pumping mechanisms which operate generally in the above described manner are fully disclosed in U.S. Pat. Nos. 2,379,539; 2,355,618; 2,428,460; 2,572,977; 2,751,848 and 3,277,381.
These prior art pumps critically depend on ideal adjustments of the input frequency relative to the length of the pump tubing in which the liquid column is contained. That is, resonant timing. Further, these prior art pumps are seriously limited as to their pumping capacity due to fluid friction, inertia of the liquid, and the like. The problems with resonant timing, frictional losses and the like have kept these prior art pumps from becoming commercially successful in general pumping applications, and they are not practical for use in low production wells due to the high gas content and low fluid flow rates in that such conditions render these pumps virtually inoperable.
Therefore, a need exists for a new and useful pump for use in low production wells which overcomes some of the problems and shortcomings of the prior art.